1. Field of the Invention
The present invention relates to improvements in the mechanism for raising and lowering the compacting ram in a compactor.
2. Description of the Prior Art
Household trash compactors typically include a cabinet having a motor driven platen or ram mounted in the upper portion which descends into a trash containing receptacle in the lower portion of the cabinet to effect compaction. The ram then retracts to the upper portion. While many mechanisms may be employed to drive the ram, the most commonly used is of the nut and lead screw type. The nut is fastened to one of the ram or cabinet. The lead screw, which passes through the nut, is fastened to the other of ram or cabinet. The nut or lead screw is rotated, producing relative axial movement between the rotating and nonrotating elements which results in a raising or lowering of the ram.
The stresses generated during trash compaction and applied to the drive means are significant, resulting in a high level of frictional forces in the drive means. These forces tend to attain peak levels as the ram reaches the bottom of its stroke against the fully compressed trash, stops, and reverses. A large amount of power is needed to overcome the static friction appearing during the stop immediately prior to reversal and prevent the ram from becoming immobilized in the lowered position in the receptacle. These power demands may necessitate the use of a bigger motor than would otherwise be necessary.
Further, the stresses generated during trash compaction are often eccentrically applied to the drive mechanism as, for example, by a soda bottle standing in one corner of the receptacle. This causes the screw to be canted in the nut creating a wedging action which further and greatly increases the frictional drag in the drive means and the power demands on the motor.
Nut and lead screw drive mechanisms have, in the past, also produced squeals and other annoying noises during compaction. The useful life of the drive mechanism is often less than desired.
The foregoing has given rise to a variety of techniques directed toward obtaining satisfactory operation of the drive means. Lubricating greases and oils may be applied to the drive means, extending its useful life, eliminating the squeaks, and reducing frictional forces. The nut may be formed of sintered metal having a high porosity for receiving and retaining a lubricant. Or, the nut may be fabricated of cast iron having a high graphite content for the same purpose. The nut and screw may be formed so that the material of one is harder than the material of the other. Exotic materials, such as vanadium alloyed steels, may be employed in the nut. The nut may be hemispherically formed to accommodate eccentric loading of the ram and drive mechanism.
While such techniques reduced or eliminated some of the foregoing shortcomings, they often did so only to the detriment of increased cost, weight, complexity, and maintenance requirements.